Common Registration Assessment, Part 1
Neonatal maintenance fluid calculations
Three original questions on maintenance fluid volumes for term neonates by day of life, with the working shown.
Published 14 October 2026. Independent revision material, not GPhC questions, not for patient care.
NICE guideline NG29 gives routine maintenance IV fluid rates for term neonates by age as a guide: birth to day 1, 50 to 60 mL/kg/day; day 2, 70 to 80; day 3, 80 to 100; day 4, 100 to 120; and days 5 to 28, 120 to 150 mL/kg/day.
The same guideline uses the Holliday-Segar formula for children and young people instead: 100 mL/kg/day for the first 10 kg, 50 mL/kg/day for the next 10 kg and 20 mL/kg/day above 20 kg. For neonates, the calculation is a range times the weight, then divided by 24 for an hourly rate.
The method
- Find the day of life and write the mL/kg/day range.
- Multiply the weight in kg by the lower and upper figures.
- Divide each daily volume by 24 to get mL/h.
- Round only at the end, and keep the range as a range unless the question gives one figure.
- If two days are compared, work out each one separately and then subtract.
Three practice questions
Work each one on paper first, then open the answer. All patients and prescriptions are fictional.
Question 1
A term neonate weighs 3.2 kg on day 2. What is the range of maintenance fluid volumes in mL/day and in mL/h?
Show the answer
Answer: 224 to 256 mL/day, which is about 9.3 to 10.7 mL/h
Working: Day 2 is 70 to 80 mL/kg/day. 3.2 × 70 = 224 mL. 3.2 × 80 = 256 mL. 224 ÷ 24 = 9.33 mL/h. 256 ÷ 24 = 10.67 mL/h.
Question 2
A term neonate weighs 3.5 kg on day 4. What is the daily range?
Show the answer
Answer: 350 to 420 mL/day
Working: Day 4 is 100 to 120 mL/kg/day. 3.5 × 100 = 350 mL. 3.5 × 120 = 420 mL.
Question 3
A term neonate weighs 3 kg. By how much does the lower end of the daily volume rise between day 3 and day 5?
Show the answer
Answer: 120 mL/day
Working: Day 3 lower end: 80 mL/kg/day × 3 = 240 mL. Day 5 lower end: 120 mL/kg/day × 3 = 360 mL. 360 - 240 = 120 mL/day.
Exam approach
Match the day of life to its range, multiply by the weight, and divide by 24 only if you need mL/h.
Where marks are lost
- Using the Holliday-Segar formula for a neonate.
- Using the wrong day of life.
- Forgetting to divide by 24 for an hourly rate.
- Reporting only one end of the range.
Frequently asked questions
Which neonates do these figures cover?
The NG29 figures are for term neonates, as a guide, and routine maintenance of this kind is calculated by age.
How do I find an hourly rate from the daily volume?
Divide the volume in mL for 24 hours by 24 to get mL/h.
Sources
- NICE, NG29 intravenous fluid therapy in children and young people in hospital
- GPhC, Common Registration Assessment specification and permitted items for 2026
The questions above are original and use fictional patients and prescriptions. PreRegExamPrep is not affiliated with or endorsed by the General Pharmaceutical Council.
Practise until the method is automatic
Try 15 free questions with worked answers. No sign-up required.
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See also the formula sheet, the eight sample questions and the approved calculator page.